In those eight years, nearly 300 optical flashes were detected, caused by small asteroids (one to 10 metres in size) exploding in the upper atmosphere. The revised estimate suggests Earth’s upper atmosphere is hit about once a year by asteroids that release energy equivalent to 5 kilotons of TNT. Larger impacts, like the 10-megaton event that leveled 2000 square metres of forest in Tunguska, Siberia in 1908 (which would level New York City), should occur once every 1000 years. This is better than the old ground-based estimate of 300 years.
Well I’ll sleep better tonight, let me tell you. How much would anyone like to wager, though, that as a result of this study, it will now be even more difficult to convince government officials to spend any money on devising asteroid defence systems?